Cervical Muscle Activity Research Articles

Cervical spinal V2a neurons pattern respiratory muscle activity and enhance ventilation

Our prior studies suggested that one subset of V2a neurons activates accessory respiratory muscles whereas another subset of V2a neurons actively prevents their activation at rest. However, since these studies altered V2a neuron excitability throughout the spinal cord and brainstem, it was not clear whether the V2a neurons that activate accessory respiratory muscles are located in the same region of the neuraxis as V2a neurons that prevent activation of accessory respiratory muscles at rest. Therefore, we used a Cre‐dependent AAV virus injected into a Chx10Cre/+ mouse to selectively target either the excitatory (Gq)‐ or inhibitory (Gi)‐DREADD receptor to cervical spinal V2a neurons on one side or both sides of the cord in order to alter V2a neuron excitability. Whole breath plethysmography (WBP) and electromyography (EMG) were recorded in conscious mice at rest to measure ventilation and respiratory muscle activity before and after altering V2a neuron excitability. We found that bilaterally increasing the excitability of cervical spinal V2a neurons increases accessory respiratory muscle (scalene) activity, diaphragm EMG peak amplitude, and ventilation. Although V2a neurons project ipsilaterally, increasing their excitability on one side of the cord is able to synchronously activate scalene muscles on both sides of the body. Bilaterally silencing cervical spinal V2a neurons also activates scalene muscle activity, but does not impair diaphragm function. Our results are consistent with the hypothesis that one subset of V2a neurons in the cervical spinal cord activates accessory respiratory muscles whereas another subset of cervical V2a neurons inhibits accessory respiratory muscles at rest.Support or Funding Information1RO1NS112255T32NS5007453University of Cincinnati Dean’s Dissertation Completion Fellowship

Positioning and baby devices impact infant spinal muscle activity

Infant positioning in daily life, particularly in relation to active neck and back muscles, may affect spinal development, psychosocial progression, and motor milestone achievement. Yet the impact of infant body position on muscle activity is unknown. The objective of this study was to evaluate neck and back muscle activity of healthy infants in common positions and baby devices.Healthy full-term infants (n = 22, 2–6 months) participated in this experimental study. Daily sleep and positioning were reported by caregivers. Cervical paraspinal and erector spinae muscle activity was measured using surface electromyography (EMG) in five positions: lying prone, lying supine, held in-arms, held in a baby carrier, and buckled into a car seat. Mean filtered EMG signal and time that muscles were active were calculated. Paired t-tests were used to compare positions to the prone condition. Caregivers reported that infants spent 12% of daily awake time prone, 43% in supine-lying baby gear, and 44% held in-arms or upright in a baby carrier. Infants exhibited highest erector spinae activity when prone, and lowest cervical paraspinal muscle activity in the car seat. No differences were found between in-arms carrying and babywearing. This first evaluation of the muscle activity of healthy infants supports the importance of prone time in infants’ early spinal development because it promotes neck and back muscle activity. Carrying babies in-arms or in baby carriers may also be beneficial to neck muscle development, while prolonged time spent in car seats or containment devices may be detrimental to spinal development.

Association of cervical spine signs and symptoms with temporomandibular disorders in adults: a systematic review protocol.

The objective of this systematic review is to assess the evidence of association of cervical spine signs and symptoms with temporomandibular disorders (TMD). This will help to lend credence to mechanisms supporting the association in order to improve care strategies for this condition. The association of cervical spine impairments (in relation to neck posture, cervical spine mobility, muscle tenderness, muscle activity, and neck disability) with TMD has been widely discussed in the literature. Clarification of this relationship is important for health professionals to better assess and treat TMD. Eligible studies will include participants aged 18 years and over, with a diagnosis of TMD from the Research and Diagnostic Criteria for Temporomandibular Disorders or a revised version. Exclusion criteria will be participants with previous temporomandibular joint surgery, history of trauma or fracture in the temporomandibular joint or the craniomandibular system; serious comorbid conditions such as cancer, rheumatic disease, and neurological problems; primary cervical spine disorders such as disc herniation or spinal degenerative changes; or systemic disease such as ankylosing spondylitis. The search for articles will be conducted in the databases PubMed, PEDro, CINAHL, Web of Science, and Embase, without language or time restrictions. Two independent reviewers will review the title, abstract, and full texts of identified studies; select studies against the inclusion criteria; assess the methodological quality of eligible studies using critical appraisal tools; and perform data extraction. Relevant quantitative data will be pooled with statistical meta-analysis, when possible. PROSPERO CRD42019123698.

Head Movements and Neck Muscle Activity During Air Combat Maneuvering.

BACKGROUND: The aim of the study was to determine the characteristics of cervical muscle activity in different head movements when using helmet mounted display in air combat maneuvering.METHODS: Cervical EMG was measured with eight F/A-18 pilots using the Joint Helmet Mounted Cueing System (JHMCS) during air combat maneuvering. In-flight Gz acceleration and continuous head position were recorded. Muscular activity was compared between head movements in isolation and combined with torso movement. In addition, the effect of the direction of head movements and the use of head support of the ejection seat on muscle activity was determined.RESULTS: Muscular loading increased in the cervical flexors and extensors when using the torso during targeting beyond the field of vision in the neutral sitting posture; the difference was significant in the flexors, but activity levels were higher in the extensors. Cervical muscles are loaded to a lesser extent if the head is kept in a stable position during Gz loading. Muscular activity in the neck muscles was higher when the pilot was moving the head out of neutral posture rather than toward neutral posture. The use of the headrest as a support decreased muscle activity in the extensors, but resulted in higher activity in the flexor muscles.DISCUSSION: All analyzed conditions were significantly affected by an increase in Gz. An increase of muscle activity with torso movements is considered as a positive factor as it reflects maintained muscular support for the cervical spine. Presented results may be helpful when specific conditioning programs and cockpit ergonomics are developed for fighter pilots.Sovelius R, Mäntylä M, Huhtala H, Oksa J, Valtonen R, Tiitola L, Leino T. Head movements and neck muscle activity during air combat maneuvering. Aerosp Med Hum Perform. 2020; 91(1):26-31.

Joint Helmet-Mounted Cueing System and Neck Muscle Activity During Air Combat Maneuvering.

BACKGROUND: The aim of the study was to determine the characteristics of cervical muscle activity in different head postures when using helmet-mounted display in one fighter vs. two aircraft air combat within visual range (WVR).METHODS: Cervical EMG was measured with eight F/A-18 pilots using the Joint Helmet Mounted Cueing System (JHMCS) during air combat maneuvering. In-flight Gz acceleration and continuous head position were recorded. EMG activity is divided and presented in a matrix with three-class rotation and five-class flexion-extension postures.RESULTS: The mean muscle activity in sternocleidomastoids and cervical extensors was 28.9% of maximal voluntary contraction (MVC) and 44.8% MVC, respectively. Cervical flexor and extensor muscles are subjected to loading over MVC during high Gz sorties. Cervical rotation combined with extension exceeded muscle force-producing capacity during high Gz, resulting in a decline in muscle activity.DISCUSSION: Awkward postures, especially rotational ones, are more prone to increase loading over muscles' capacity. Overloading of muscles increases the risk of muscular and ligamentous injury. In addition, the lack of muscular support potentially leads to the Gz loading being transferred to spinal structures via intervertebral discs and the vertebral column. The JHMCS helmet seems to change the pattern of most loading muscles toward the extensor (posterior) neck muscles.Sovelius R, Mäntylä M, Heini H, Oksa J, Valtonen R, Tiitola L, Leino T. Joint helmet-mounted cueing system and neck muscle activity during air combat maneuvering. Aerosp Med Hum Perform. 2019; 90(10):834-840.

Cervical Rotator Muscle Activity With Eye Movement at Different Speeds is Distorted in Whiplash.

People with whiplash-associated disorders (WADs) report difficulty with quick head movements and cervicoocular dysfunction. Changes in coordination between eye movement and neck muscle activity may be involved. To examine whether activity of superficial and deep neck muscles increases with eye movement when the head is held in a fixed position, whether this differs between directions and speed of eye movement, and whether this is modified in WAD. Convenience case series with unmatched controls. Research laboratory. Nine individuals with chronic WAD grade II and 11 pain-free controls. Electromyography (EMG) was recorded from muscles that could act to rotate the neck to the right (right obliquus capitis inferior [OI], multifidus [MF], splenius capitis [SC], and left sternocleidomastoid [SCM]) with intramuscular or surface electrodes in 9 WAD participants and 11 pain-free controls. Eyes were rotated without head movement to track slow and medium-speed targets to the right or left, and as fast as possible (FP). Amplitude of EMG. In controls, SCM and SC EMG increased with right gaze (all P's < .03). EMG of the deep OI muscle increased in both directions (P < .001). WAD involved counterintuitive greater activity of SCM with left rotation across speeds of eye movement (SC with slow movement, P < .036), decreased OI EMG with gaze left (P < .019), and no change in MF EMG (P < .6) in either gaze direction. For FP tasks, EMG of all muscles was greater than slower speeds in controls (all P's < .0001), but not WAD (all P's > .33). Coordination between neck muscle activity and eye movements with increasing speed is modified in WAD. Contrasting changes are present in deep and superficial neck muscles with implications for neck function that may explain some common WAD symptoms. IV.

Experimental and Numerical Study of Cervical Muscle Contraction in Frontal Impact

In a crash situation, drivers typically make evasive maneuvers before an upcoming impact, which can affect the kinematics and injury during impact. The purpose of the current study was to investigate the response and effect of drivers’ cervical muscles in a frontal impact. A crash scenario was developed using a vehicle driving simulator, and 10 volunteers were employed to drive the simulator at 20 km/h, 50 km/h, 80 km/h and 100 km/h. Electromyography (EMG) was recorded from the sternocleidomastoideus (SCM), splenius cervicis (SPL) and trapezium (TRP) muscles using a data acquisition system, and the level of muscle activation was calculated. A numerical study was conducted using data collected in the experiment. The results revealed that the cervical muscles were activated during drivers’ protective action. EMG activity of cervical muscles before impact was greater than that during normal driving. EMG activity increased with driving speed, with the SCM and TRP exhibiting larger increases than the SPL. The kinematics and load of the driver were influenced by muscle activation. Before the collision, the head of an active model stretched backward, while the passive model kept the head upright. In low-speed impact, the torque and shear of the cervical muscle in the active model were much lower than those in the passive model, while the tension of the cervical muscle was higher in the active model compared with the passive model. The results indicated that the incidence of cervical injury in high-speed impact is complex.

History of concussion is associated with higher head acceleration and reduced cervical muscle activity during simulated rugby tackle: An exploratory study

ObjectivesThe objective of this study is to explore the effect of concussion history on head control during front on rugby tackles in non-professional male and female Rugby Union players. DesignAn observational cross-sectional design. SettingA laboratory-based study of simulated front on rugby tackles with a dynamic relatively-weighted (∼50% body-mass) tackle bag. Participants27 club Rugby Union players were recruited; 10 (7female) with no-concussion history, 10 (3female) within 12-months of concussion and 7 (3female) with 24 + months since last concussion. Main outcome measuresLinear and rotational head acceleration measured with a skin mounted CSx® triaxial accelerometer. Normalized Surface EMG amplitude of the bilateral sternocleidomastoid (Scm), upper trapezius (Trap) and splenius capitis (Spl). All outcome measures were synchronised with moment of impact with the tackle bag. ResultsA mixed-model analysis showed that players with 12-Month concussion history had the highest head acceleration (females = 48.6g, males = 68.3g, p < 0.05) with lower Trap (6.9–11.7%, p < 0.05) and Spl (3–12%, p < 0.05) amplitudes compared to athletes with No-concussion. ConclusionsThese findings suggest probable disruption to neuromuscular control of the head in athletes with concussion history as a potential mechanism for recurrent concussion incidence.

Comparison of the muscle activity in the normal and forward head postures based on the pressure level during cranio-cervical flexion exercises

Purpose: This paper proposes proper and effective neck exercises by comparing the deep and superficial cervical flexor muscle activities and thickness according to the pressure level during cranio-cervical flexion exercises between a normal posture group and forward head posture group. Methods: A total of 20 subjects (8 males and 12 females) without neck pain and disabilities were selected. The subjects’ craniovertebral angles were measured; they were divided into a normal posture and a forward head posture group. During cranio-cervical flexion exercises, the thickness of the deep cervical flexor neck muscle and the activity of the surface neck muscles were measured using ultrasound and EMG. Results: The results showed that the thickening of the deep cervical flexor was increased significantly to 28 and 30 mmHg in the forward head posture group. The sternocleidomastoid muscle activity increased significantly to 24, 26, 28, and 30 mmHg in the forward head posture group. The anterior scalene muscle activity increased significantly to 26, 28, and 30mmHg in the forward head posture group. A significant difference of 26, 28, and 30 mmHg in the sternocleidomastoid and anterior scalene muscles was observed between two groups. Conclusion: To prevent a forward head posture and maintain proper cervical curve alignment, the use of the superficial cervical flexor muscles must be minimized. In addition, to perform a cranio-cervical flexion exercises to effectively activate the deep cervical flexor muscles, 28 and 30 mmHg for normal posture adults and 28 mmHg for adults with forward head postures are recommended.

The role of cervical muscles in mitigating concussion

ObjectivesIncreased neck strength has been hypothesized to lower sports related concussion risk, but lacks experimental evidence. The goal is to investigate the role cervical muscle strength plays in blunt impact head kinematics and the biofidelity of common experimental neck conditions. We hypothesize head kinematics do not vary with neck activation due to low short term human head-to-neck coupling; because of the lack of coupling, free-head experimental conditions have higher biofidelity than Hybrid III necks. MethodsImpacts were modeled using the Duke University Head and Neck Model. Four impact types were simulated with six neck conditions at eight impact positions. Peak resultant linear acceleration, peak resultant angular acceleration, Head Injury Criterion, and Head Impact Power compared concussion risk. To determine significance, maximum metric difference between activation states were compared to critical effect sizes (literature derived differences between mild and severe impact metrics). ResultsMaximum differences between activation conditions did not exceed critical effect sizes. Kinematic differences from impact location and strength can be ten times cervical muscle activation differences. Hybrid III and free-head linear acceleration metrics were 6±1.0% lower and 12±1.5% higher than relaxed condition respectively. Hybrid III and free-head angular acceleration metrics were 12±4.0% higher and 2±2.7% lower than relaxed condition respectively. ConclusionsResults from a validated neck model suggest increased cervical muscle force does not influence short term (<50ms) head kinematics in four athletically relevant scenarios. Impact location and magnitude influence head kinematics more than cervical muscle state. Biofidelic limitations of both Hybrid III and free-head experimental conditions must be considered.

Effects of cranio-cervical flexion with transcranial direct current stimulation on muscle activity and neck functions in patients with cervicogenic headache.

[Purpose] To present an efficient treatment regimen for patients with cervicogenic headache by comparatively analyzing the neck disability index (NDI) and cervical muscle activity after an exercise intervention. [Participants and Methods] Thirty patients with cervicogenic headache were assigned to the cranio-cervical flexion group (n=15) and cranio-cervical flexion plus transcranial direct current stimulation (tDCS) group (n=15). Intervention was administered for four weeks, after which the participants’ NDI and sternocleidomastoid muscle activity were measured. [Results] The treatment group demonstrated a significantly greater change in NDI after the intervention compared to the control group. The treatment group also showed a significantly greater change in sternocleidomastoid muscle activity than the control group. [Conclusion] Our results show that applying tDCS during cranio-cervical flexion exercise can strengthen the sternocleidomastoid muscle more effectively while improving pain and associated functions in patients with cervicogenic headache. These results would contribute towards developing a more efficient treatment for patients with cervicogenic headache.

Head impact analysis in elite football (soccer)

IntroductionTrauma related neuropathologies including recent reports involving chronic traumatic encephalopathy (CTE) in 8 soccer players have been concerning. Purposeful sub-concussive head impacts, known as headers, are an integral part of the game. The purpose of this study was to describe dynamic head response and brain tissue strains for front ball-to-head impacts in elite soccer.MethodsVideo analysis thirteen (13) Champion's League soccer footage was completed to establish reconstruction parameters of head impact events. Analysis of 5 (5) front ball-to-head events were reconstructed using a Hybrid III 50th percentile headform and a pneumatic linear impactor. The University College Dublin Brain Trauma Model was used to calculate maximum principal strain (MPS).Results and discussionRecorded head impact velocities during elite soccer game play were 3.5–23.0 m/s. Most purposeful head-to-ball impacts occurred on the front-temporal region of the head (66.4%) at 0–15 degrees of cervical flexion. There was an average of 1.5 unintentional head impacts and 62.2 headers per game; 49.6% of headers occurred at an inbound velocity below 10 m/s. The lowest velocity reconstructed was 4.7 m/s, yielding 12.8 g and 604 rad/s2 for peak resultant linear and rotational accelerations, respectively; the MPS for this impact was 0.09. Neurophysiologic changes and functional impairment have been reported in past research on sub-concussive impacts with 5%–15% strain. The mean 0.11 MPS yielded in this study reflects a potential for these changes in elite soccer athletes.ConclusionThe main objective of this analysis was to identify impact characteristics and quantify dynamic cerebral response and brain tissue deformation in elite soccer game play. Further research must include cervical muscle activation, the level of play and player position, inbound ball-to-head velocities during different game play events and appropriate impact characteristics to appropriately characterize risk of injury in the attempts of mitigating risk of head injury during soccer game play.

The neutral posture of the cervical spine is not unique in human subjects

Cervical spine injuries often happen in dynamic environments (e.g., sports and motor vehicle crashes) where individuals may be moving their head and neck immediately prior to impact. This motion may reposition the cervical vertebrae in a way that is dissimilar to the upright resting posture that is often used as the initial position in cadaveric studies of catastrophic neck injury. Therefore our aim was to compare the “neutral” cervical alignment measured using fluoroscopy of 11 human subjects while resting in a neutral posture and as their neck passed through neutral during the four combinations of active flexion and extension movements in both an upright and inverted posture. Muscle activation patterns were also measured unilaterally using surface and indwelling electromyography in 8 muscles and then compared between the different conditions. Overall, the head posture, cervical spine alignment and muscle activation levels were significantly different while moving compared to resting upright. Compared to the resting upright condition, average head postures were 6–13° more extended, average vertebral angles varied from 11° more extended to 10° more flexed, and average muscle activation levels varied from unchanged to 10% MVC more active, although the exact differences varied with both direction of motion and orientation. These findings are important for ex vivo testing where the head and neck are statically positioned prior to impact – often in an upright neutral posture with negligible muscle forces – and suggest that current cadaveric head-first impact tests may not reflect many dynamic injury environments.

Wednesday, September 26, 2018 7:35 AM–9:00 AM ePosters: P10. Infant positioning impacts neck and back muscle activity: a pilot study exploring implications for spinal development

BACKGROUND CONTEXT Since 1992, pediatricians have recommended that all infants be placed to sleep in the supine or side-lying position to reduce the risk of Sudden Infant Death Syndrome (SIDS). Although this policy successfully reduced the incidence of SIDS by nearly 50%, questions regarding the positional impact on musculoskeletal and motor development have since surfaced. Studies have linked prone positioning to extensor muscle development and motor milestone achievements, and some believe a link can be made between infant positioning and idiopathic infantile scoliosis. Recently, a relationship between muscle forces and spinal curvatures, particularly hyperkyphosis, was found in fetal chicks, leading to more questions regarding the role of the paraspinal muscles in early spinal development/deformity. PURPOSE The purpose of this pilot study is to examine relationships between infant positions and neck or back muscle activity using electromyography (EMG). STUDY DESIGN/SETTING Electromyographic research study. PATIENT SAMPLE Healthy infants aged 2-7 months. OUTCOME MEASURES Normalized mean EMG data. METHODS Seven healthy infants (mean 5.2 months, 5 male) were enrolled in the study. Surface EMG recorded muscle activity of bilateral cervical paraspinal and erector spinae muscles during five 30-second tasks: laying prone, laying supine, held in arms, held in a baby carrier, and in a car seat. EMG data was normalized to the prone task, and paired t-tests were used to compare to the prone position (p RESULTS Infants exhibited significantly more erector spinae activity during prone positioning compared to all other tasks, and twice as much compared to the supine position (p CONCLUSIONS This first look at the muscle activity of healthy infants in common positions supports the importance of prone time in neck and back development. Prone time significantly increases erector spinae activity. As subject enrollment continues, the in-carrier position may show comparable neck muscle activity to the prone position, as the baby must support the weight of the head while upright.

Resting cranial and upper cervical muscle activity is increased in patients with migraine

ObjectiveTo compare comprehensive measures of scalp-recorded muscle activity in migraineurs and controls. MethodWe used whole-of-head high-density scalp electrical recordings, independent component analysis (ICA) and spectral slope of the derived components, to define muscle (electromyogram-containing) components. After projecting muscle components back to scalp, we quantified scalp spectral power in the frequency range, 52–98 Hz, reflecting muscle activation. We compared healthy subjects (n = 65) and migraineurs during a non-headache period (n = 26). We also examined effects due to migraine severity, gender, scalp-region and task (eyes-closed and eyes-open). We could not examine the effect of pre-ictal versus inter-ictal versus post-ictal as this information was not available in the pre-existing dataset. ResultsThere was more power due to muscle activity (mean ± SEM) in migraineurs than controls (respectively, −13.61 ± 0.44 dB versus −14.73 ± 0.24 dB, p = 0.028). Linear regression showed no relationship between headache frequency and muscle activity in any combination of region and task. There was more power during eyes-open than eyes-closed (respectively, −13.42 ± 0.34 dB versus −14.92 ± 0.34 dB, p = 0.002). ConclusionsThere is an increase in cranial and upper cervical muscle activity in non-ictal migraineurs versus controls. This raises questions of the role of muscle in migraine, and the possible differentiation of non-ictal phases. SignificanceThis provides preliminary evidence to date of possible cranial muscle involvement in migraine.

Asymmetry of neck motion and activation of the cervical paraspinal muscles during prone neck extension in subjects with unilateral posterior neck pain.

Although unilateral posterior neck pain (UPNP) is more prevalent than central neck pain, little is known about how UPNP affects neck motion and the muscle activation pattern during prone neck extension. To investigate whether deviation in neck motion and asymmetry of activation of the bilateral cervical paraspinal muscles occur during prone neck extension in subjects with UPNP compared to subjects without UPNP. This study recruited 20 subjects with UPNP and 20 age- and sex-matched control subjects without such pain. Neck motion and muscle onset time during prone neck extension were measured using a three-dimensional motion-analysis system and surface electromyography. The deviation during prone neck extension was greater in the UPNP group than in the controls (p < 0.05). Compared with the controls, cervical extensor muscle activation in the UPNP group was significantly delayed on the painful side during prone neck extension (p < 0.05). Subjects with UPNP showed greater asymmetry of neck motion and muscle activation during prone neck extension compared with the controls. This suggests that UPNP has specific effects on neck motion asymmetry and the functions of the cervical extensors, triggering a need for specific evaluation and exercises in the management of patients with UPNP.

Cervical stability training with and without core stability training for patients with cervical disc herniation: A randomized, single-blind study.

This study aims at evaluating and comparing the effects of cervical stability training to combined cervical and core stability training in patients with neck pain and cervical disc herniation. Fifty patients with neck pain and cervical disc herniation were included in the study, randomly divided into two groups as cervical stability and cervical-core stability. Training was applied three times a week in three phases, and lasted for a total duration of 8weeks. Pain, activation and static endurance of deep cervical flexor muscles, static endurance of neck muscles, cross-sectional diameter of M. Longus Colli, static endurance of trunk muscles, disability and kinesiophobia were assessed. Pain, activation and static endurance of deep cervical flexors, static endurance of neck muscles, cross-sectional diameter of M. Longus Colli, static endurance of trunk muscles, disability and kinesiophobia improved in both groups following the training sessions (p<0.05). Comparison of the effectiveness of these two training methods revealed that the cervical stability group produced a greater increase in the right transverse diameter of M. Longus Colli (p<0.05). However, static endurance of trunk muscles and kinesiophobia displayed better improvement in the cervical-core stability group (p<0.05). Cervical stability training provided benefit to patients with cervical disc herniation. The addition of core stability training did not provide any additional significant benefit. Further research is required to investigate the efficacy of combining other techniques with cervical stability training in patients with cervical disc herniation. Both cervical stability training and its combination with core stability training were significantly and similarly effective on neck pain and neck muscle endurance in patients with cervical disc herniation.

A Comparative Study in Cervical Muscle Activities during Various Resting Postures Using Electromyography

A Comparative Study in Cervical Muscle Activities during Various Resting Postures Using Electromyography

Evaluation of a minimum-norm based beamforming technique, sLORETA, for reducing tonic muscle contamination of EEG at sensor level

BackgroundCranial and cervical muscle activity (electromyogram, EMG) contaminates the surface electroencephalogram (EEG) from frequencies below 20 through to frequencies above 100Hz. It is not possible to have a reliable measure of cognitive tasks expressed in EEG at gamma-band frequencies until the muscle contamination is removed. New methodIn the present work, we introduce a new approach of using a minimum-norm based beamforming technique (sLORETA) to reduce tonic muscle contamination at sensor level. Using a generic volume conduction model of the head, which includes three layers (brain, skull, and scalp), and sLORETA, we estimated time-series of sources distributed within the brain and scalp. The sources within the scalp were considered to be muscle and discarded in forward modelling. Result(1) The method reduced EMG contamination, more strongly at peripheral channels; (2) task-induced cortical activity was retained or revealed after removing putative muscle activity. Comparison with existing methodsThis approach can decrease tonic muscle contamination in scalp measurements without relying on time-consuming processing of expensive MRI data. In addition, it is competitive to ICA in muscle reduction and can be reliably applied on any length of recorded data that captures the dynamics of the signals of interest. ConclusionThis study suggests that sLORETA can be used as a method to quantitate cranial muscle activity and reduce its contamination at sensor level.

Effects of Dual Monitor Computer Work Versus Laptop Work on Cervical Muscular and Proprioceptive Characteristics of Males and Females.

The effects of performing a 90-minute computer task with a laptop versus a dual monitor desktop workstation were investigated in healthy young male and female adults. Work-related musculoskeletal disorders are common among computer (especially female) users. Laptops have surpassed desktop computer sales, and working with multiple monitors has also become popular. However, few studies have provided objective evidence on how they affect the musculoskeletal system in both genders. Twenty-seven healthy participants (mean age = 24.6 years; 13 males) completed a 90-minute computer task while using a laptop or dual monitor (DualMon) desktop. Electromyography (EMG) from eight upper body muscles and visual strain were measured throughout the task. Neck proprioception was tested before and after the computer task using a head-repositioning test. EMG amplitude (root mean square [RMS]), variability (coefficients of variation [CV]), and normalized mutual information (NMI) were computed. Visual strain ( p < .01) and right upper trapezius RMS ( p = .03) increased significantly over time regardless of workstation. Right cervical erector spinae RMS and cervical NMI were smaller, while degrees of overshoot (mean = 4.15°) and end position error (mean = 1.26°) were larger in DualMon regardless of time. Effects on muscle activity were more pronounced in males, whereas effects on proprioception were more pronounced in females. Results suggest that compared to laptop, DualMon work is effective in reducing cervical muscle activity, dissociating cervical connectivity, and maintaining more typical neck repositioning patterns, suggesting some health-protective effects. This evidence could be considered when deciding on computer workstation designs.